Expression of the myc proto-oncogenes in developing human fetal brain.
We have analysed c-myc, N-myc and L-myc gene expression in developing human fetal brain by Northern hybridization, RNAase protection and in situ hybridization. The unique zonal organization of the developing fetal brain allows a particularly good assessment of the coupling of myc gene expression to cell proliferation and differentiation in vivo. By Northern and in situ hybridization, L-myc as well as c-myc and N-myc transcripts in the brain were found in the post-mitotic cortical and intermediate layers, as well as in the mitotically active layers containing the neuroepithelial precursor cells. Consistent results were also obtained for L-myc using RNAase protection analysis. Both the 3.6 and 3.8kb forms of the L-myc mRNA, resulting from alternative splicing of intron I, were detected in layers of neuroectodermal origin, but not in the meninges or choroid plexus. We also extended L-myc expression and splicing analyses to other developing human fetal tissues. L-myc mRNA was expressed in several other fetal tissues, particularly in fetal skin. Predominantly intron I containing L-myc mRNA was observed in fetal striated and cardiac muscle. Thus, L-myc is expressed in a wider spectrum of developing tissues than previously known. Our findings also, show that L-myc as well as N-myc and c-myc expression is uncoupled from cell division in developing brain.
Hirvonen
H
H
Department of Medical Biochemistry, University of Turku, Finland.
Mäkelä
T P
TP
Sandberg
M
M
Kalimo
H
H
Vuorio
E
E
Alitalo
K
K
D015152:Blotting, Northern; D001921:Brain / Q000196:embryology / Q000378:metabolism* / Q000502:physiology; D002490:Central Nervous System / Q000196:embryology / Q000378:metabolism / Q000502:physiology; D005314:Embryonic and Fetal Development / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007381:Intermediate Filament Proteins / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014746:Vimentin / Q000235:genetics / Q000378:metabolism
D007381:Intermediate Filament Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D014746:Vimentin